1. Field of the Invention
The present invention relates to a plasma display panel (PDP) with improved energy recovery efficiency, and a driving method thereof.
2. Description of the Related Art
A PDP is a display device for restoring image data input as an electrical signal by arranging a plurality of discharge tubes in a matrix to selectively emit light. PDPs are largely classified into direct current (DC) type PDPs and alternating current (AC) type PDPs according to whether the polarity of the voltage applied for sustaining a discharge changes or not over time.
FIG. 1 shows the basic structure of a general AC face discharge PDP. Referring to FIG. 1, a discharge space 15 is formed between a front glass substrate 11 and a rear glass substrate 17. In the AC face discharge PDP, a discharge sustaining electrode 12 is covered by a dielectric layer 13 so as to be electrically isolated from the discharge space 15. In this case, a discharge is sustained by the well-known wall charge effect. The above-described face discharge PDP includes two parallel discharge sustaining electrodes 12 formed on the front substrate 11 and an address electrode 16 formed on the rear substrate 17 so as to be orthogonal to the discharge sustaining electrodes 12. According to this structure, an address discharge in which a pixel is selected occurs between the address electrode 16 and the discharge sustaining electrodes 12, and then a sustained discharge in which a video signal is displayed occurs between the two discharge sustaining electrodes 12, that is, between a common (X) electrode 12a and a scanning (Y) electrode 12b. 
FIG. 2 is an exploded perspective view schematically illustrating a generally used AC three-electrode face discharge PDP, in which an address electrode 16 and a pair of discharge sustaining electrodes 12a and 12b perpendicular to the address electrode 16 are installed for each discharge space 15 which is divided by partitions 18 formed on a rear substrate 17. The partitions 18 serve to block space charges and ultraviolet rays produced during a discharge, to thus prevent cross talk from being generated at neighboring pixels, as well as to form the discharge spaces 15. In order for a PDP to operate as a color display device, fluorescent material layers 19 made of a fluorescent material excited by the ultraviolet rays produced during discharge and having red (R), green (G) and blue (B) visible ray emitting characteristics, for displaying R, G and B colors, are sequentially coated in the discharge spaces 15 in order, thereby displaying R, G and B colors.
In order for a fluorescent-material-coated PDP to be capable of operating as a color video display device, a gray scale display must be utilized. Currently, a gray scale display method in which a picture of one frame is divided into a plurality of sub-fields to then be driven in a time-division manner is widely used.
FIG. 3 shows a gray scale display method in a general AC PDP. As shown in FIG. 3, in the gray scale display method of a general AC PDP, a picture of one frame is divided into a plurality of sub-fields each consisting of address periods and sustained discharge periods. Here, a 6-bit gray scale implementation method, for example, is explained. A picture of a frame is temporally divided into six sub-fields and 64 (=26) gray scales are displayed. Each sub-field consists of address periods A1-A6 and sustained discharge periods S1-S6. Gray scales are displayed using a principle in which the comparative lengths of the sustained discharge periods are expressed visually in the brightness ratio. In other words, since the lengths of the sustained discharge periods S1 to S6 of the first sub-field (SF1) to the sixth sub-field (SF6) comply with a ratio of 1:2:4:8:16:32, altogether, 64 types of sustained discharge periods, that is, 0, 1(1T), 2(2T), 3(1T+2T), 4(4T), 5(1T+4T), 6(2T+4T), 7(1T+2T+4T), 8(8T), 9(1T+8T), 10(2T+8T), 11(3T+8T), 12(4T+8T), 13(1T+4T+8T), 14(2T+4T+8T), 15(1T+2T+4T+8T), 16(16T), 17(1T+16T), 18(2T+16T), . . . , 62(2T+4T+8T+16T+32T) and 63(1T+2T+4T+8T+16T+32T) are constituted, thereby displaying 64 gray scale levels. For example, in order to display a gray scale level of 6 at an arbitrary pixel, only the second sub-field (2T) and the third sub-field (4T) have to be addressed. Also, in order to display a gray scale level of 15, all of the first through fourth sub-fields have to be addressed.
FIG. 4 is a layout diagram of electrodes of an AC face discharge PDP constructed for implementation of the gray scale display method shown in FIG. 3. Here, among the discharge sustaining electrodes 12, consisting of paired horizontal electrodes, the interconnected electrodes are common electrodes (X-electrodes) 12a and the other side electrodes are scanning electrodes (Y-electrodes) 12b. The common electrodes (X-electrodes) 12a are all connected together, and a voltage signal, including a discharge sustain pulse, is applied thereto. Thus, a scanning signal is applied to the scanning electrodes, that is, the Y-electrodes 12b, so that addressing is done between the Y-electrodes 12b and the address electrodes 6, and the discharge sustain pulse is applied between the Y-electrodes 12b and the X-electrodes 12a so that a display discharge is sustained. Waveforms of the driving signals applied to the respective electrodes connected as above are shown in FIG. 5.
FIG. 5 is a diagram showing the waveforms of driving signals of a generally used AC PDP, in which a picture display is implemented by an address/display separation (ADS) driving method. In FIG. 5, reference mark A denotes a driving signal applied to address electrodes, reference mark X denotes a driving signal applied to the common electrodes (to be also referred to as X-electrodes) 12a, and reference marks Y1 through Y480 denote driving signals applied to the respective Y-electrodes 12b. During a total erase period A11 a total erase pulse 22a is applied to the common (X) electrodes 12a for an accurate gray scale display to cause a strong discharge, thereby erasing wall charges generated by a previous discharge to promote the operation of the next sub-field (step 1). Next, during a total write period A12 and a total erase period A13, in order to reduce an address pulse voltage 21, a total write pulse 23 is applied to the Y-electrodes 12b and a total erase pulse 22b is applied to the X-electrodes 12a to cause a total write discharge and a total erase discharge, respectively, thereby controlling the amount of wall charges accumulated in the discharge space 15 (steps 2 and 3). Then, during an address period A14, data converted into an electrical signal is written on a selected location on the whole screen of the PDP by a selective discharge using the address pulse (data pulse) 21 and a write pulse 24 between the address electrode 16 and the scanning electrode 12b intersecting each other (step 4). Next, during a sustained discharge period S1, a display discharge, which is caused by continuously applying the discharge sustain pulse 25, is sustained for a given period of time, for the purpose of displaying picture data on the screen.
As shown, as the number of scanning lines increases, the time required for a write operation increases and the number of sub-fields increases so that the time allocated to the sustain discharge is reduced. Thus, a panel having a higher resolution has a lesser overall luminance. That is, for a high-resolution display, luminance degradation cannot be avoided.
FIG. 6 is a schematic perspective plan view illustrating the structure of a conventional three-electrode face discharge PDP. As described above, an address electrode 16 is formed on a rear glass substrate 17, and the address electrode 16 extends to either the top or bottom edges of, or to both the top and bottom edges of the rear glass substrate 17. The address electrode 16 is generally connected to an address driving board (not shown) using a flexible printed circuit (FPC). Scanning electrodes 12b and common electrodes 12a for a sustained discharge extend to both sides of the front glass substrate 11. The common electrodes 12a may be internally connected or may be connected on a driving board so as to be operable together. In order for terminals to extend outside to be connected, as shown in FIG. 6, an area corresponding to a predetermined space cannot contribute to a discharge. In FIG. 6, areas 20 indicated by dotted lines are non-luminous areas. The rear glass substrate 12 having the address electrode 16 has a non-luminous area narrower than the front glass substrate 11.
FIG. 7 illustrates the flow of current generated when the PDP undergoes a sustained discharge. During a sustained discharge, a voltage exceeding a minimum sustained discharge causing voltage is abruptly applied to scanning electrodes or common electrodes. Thus, current flows throughout a driving board 60, a frame 50 and a panel 40 just like a temporary solenoid. An electrical field is formed due to such a current flow, thereby causing electromagnetic interference (EMI).
To solve the above problems, it is an object of the present invention to provide a plasma display panel (PDP) with improved energy recovery efficiency by which EMI generated at the PDP can be offset by an electrical field generated during a sustained discharge, the number of terminals connected to common electrodes can be reduced by minimizing the current flowing in the common electrodes without applying a voltage to the common electrodes during a sustained discharge, the PDP can be tiled by minimizing the non-luminous area of the PDP, and a driving method thereof.
Accordingly, to achieve the above object, there is provided a PDP having front and rear substrates opposed to and spaced apart from each other to maintain a discharge space, discharge sustaining electrodes having pairs of parallel, striped scanning lines and common lines on the front substrate, address electrodes arranged on the rear substrate orthogonally to the discharge sustaining electrodes, and a frit portion for hermetically sealing edges of the front and rear substrates, wherein a common connection line for connecting the common electrodes with each other is formed at a periphery at one end of the front substrate, the common connection line by-passes the discharge sustaining electrodes to extend to the exposed portions of the other ends of the front substrate, in which external connection terminals, where the scanning electrodes are connected to the outside, are formed, and external connection terminals, where the common electrodes are connected to the outside, are formed at the exposed portions of the other ends of the front substrate.
Also, in the present invention, the common connection line is preferably formed at a location corresponding to the frit portion to be wider than each of the common electrodes, and the address electrodes preferably have connection terminals formed only at the exposed portions of a periphery at one end of the rear substrate.
Also, according to another aspect of the present invention, there is provided a PDP having front and rear substrates opposed to and spaced apart from each other to maintain a discharge space, discharge sustaining electrodes having pairs of parallel, striped scanning lines and common lines on the front substrate, and address electrodes arranged on the rear substrate orthogonally to the discharge sustaining electrodes, wherein external connection terminals, where the scanning and common electrodes are connected to the outside, are formed only at the exposed portions of the one-end periphery of the front substrate.
In the present invention, the external connection terminals are preferably arranged at the exposed portions of a periphery at one end of the front substrate such that they alternately connect the scanning electrodes and the common electrodes, and the address electrodes preferably have connection terminals for being connected to the outside, formed only at a periphery at one end of the rear substrate.
Alternatively, the present invention provides a PDP having front and rear substrates opposed to and spaced apart from each other to maintain a discharge space, discharge sustaining electrodes having pairs of parallel, striped scanning lines and common lines on the front substrate, address electrodes arranged on the rear substrate orthogonally to the discharge sustaining electrodes, and a frit portion for hermetically sealing edges of the front and rear substrates, wherein a common connection line for connecting the common electrodes to each other is formed at a periphery at one end of the front substrate, and external connection terminals, where a plurality of common electrodes constituting an electrode group are simultaneously connected to the outside, the extending connection terminals extending from each of the plurality of common electrodes, are formed at the exposed portions of the other ends of the front substrate, at which the external connection terminals where the scanning electrodes are connected to the outside, are formed.
In the present invention, the common connection line is preferably formed at a location corresponding to the frit portion to be wider than each of the common electrodes, and the address electrodes preferably have connection terminals formed only at the exposed portions of the one-end periphery of the rear substrate.
Also, the present invention provides a method of driving a PDP having front and rear substrates opposed to and spaced apart from each other to maintain a discharge space, discharge sustaining electrodes having pairs of parallel, striped scanning lines and common lines on the front substrate, address electrodes arranged on the rear substrate orthogonally to the discharge sustaining electrodes, and a frit portion for hermetically sealing edges of the front and rear substrates, wherein a common connection line for connecting the common electrodes to each other is formed at a periphery at one end of the front substrate, and external connection terminals, where a plurality of common electrodes constituting an electrode group are simultaneously connected to the outside, the extending connection terminals extending from each of the plurality of common electrodes, are formed at the exposed portions of the other ends of the front substrate, at which the external connection terminals where the scanning electrodes are connected to the outside, are formed, the method comprising the step of driving the scanning electrodes by each two adjacent lines, wherein positive and negative discharge sustain pulses are alternately applied to two even-numbered driven lines, and a discharge sustain pulse having an opposite polarity to the two even-numbered driven lines is applied to two odd-numbered driven lines in synchronization with the discharge sustain pulses applied to the two even-numbered driven lines.
In the present invention, when a sustained discharge is performed by the two even-numbered driven lines and the two odd-numbered driven lines, a difference in the potential therebetween is preferably 2 times the voltage of the discharge sustain pulse, and the potential of the common electrodes is preferably an intermediate level of the voltages of the discharge sustain pulses applied to the two even-numbered driven lines and the two odd-numbered driven lines.